[ " ] 



the other capftan head T ; the application of the other capftan 

 lieaded fcrew D, with its fetting fcrew, will be fhevvn in the 

 application of the adjufting tool. 



On the top of each pillar is a brafs cock marked C, and feen 

 in profile, and of a larger fize in Fig. IV. ; in this the fcrew 

 X works vertically, and is fet by the fcrew Y. 



E G F H I is a frame covered with green filk to fcreen 

 the axis from the fun *. K, K are holes in the filk to let the 

 hooks of the counterpoifes through, to relieve the Y plates from 

 the entire weight of the inftrument. 



Plate III. Fig. I. fhews the adjufting tool, the notches N, N, 

 cut in the end of the horizontal arm, reft upon the prifmatic 

 bar fhewn in the former figure, and the extremity Z, of the 

 horizontal bar at right angles to this, refts upon the point of 

 the vertical fcrew, which works in the gock C, on the oppofite 

 pillar. C, P is a fine filver wire, fupporting the plummet P, 

 which fwings in a glafs vefiTel filled with water, as is ufually 

 done to check the vibration. X, X are the two microfcopes, 

 into the focus of which the wire is brought by the fcrew C, 

 fhewn more diftindly in Fig. II. in which D is the head of a 

 fmall fcrew, which confines the end of the plumb-line under 

 its fhoulder, the plumb-line hangs through the hole H, and 

 refts in a fine notch cut in the chamfered edge S, S. The fcrew 

 B draws the whole fyftem L M N R eaft or weft, to draw 



* The view of the counterpoifes h hers omitted, not to cnibarrafs the figure. 



the 



